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HttpSecureCookie, A Way to Encrypt Cookies with ASP.NET 2.0

, 3 Apr 2006 Ms-PL 194.7K 3.1K 110
Discussing how to encode and tamper-proof text and cookies using the MachineKey, by using reflection.
httpsecurecookie_demo.zip
Bin
AdamTibi.Web.Security.dll
httpsecurecookie_src.zip
Release
AdamTibi.Web.Security.dll
Properties
using System;
using System.Web.Security;
using System.Text;

namespace AdamTibi.Web.Security {
    
    /// <summary>
    /// A class to encode, decode and validate strings based on the MachineKey
    /// </summary>
    public static class MachineKeyCryptography {

        /// <summary>
        /// Encodes a string and protects it from tampering
        /// </summary>
        /// <param name="text">String to encode</param>
        /// <returns>Encoded string</returns>
        public static string Encode(string text) {
            return Encode(text, CookieProtection.All);
        }

        /// <summary>
        /// Encodes a string
        /// </summary>
        /// <param name="text">String to encode</param>
        /// <param name="cookieProtection">The method in which the string is protected</param>
        /// <returns></returns>
        public static string Encode(string text, CookieProtection cookieProtection) {
            if (string.IsNullOrEmpty(text) || cookieProtection == CookieProtection.None) {
                return text;
            }
            byte[] buf = Encoding.UTF8.GetBytes(text);
            return CookieProtectionHelperWrapper.Encode(cookieProtection, buf, buf.Length); 
        }

        /// <summary>
        /// Decodes a string and returns null if the string is tampered
        /// </summary>
        /// <param name="text">String to decode</param>
        /// <returns>The decoded string or throws InvalidCypherTextException if tampered with</returns>
        public static string Decode(string text) {
            return Decode(text, CookieProtection.All);
        }

        /// <summary>
        /// Decodes a string
        /// </summary>
        /// <param name="text">String to decode</param>
        /// <param name="cookieProtection">The method in which the string is protected</param>
        /// <returns>The decoded string or throws InvalidCypherTextException if tampered with</returns>
        public static string Decode(string text, CookieProtection cookieProtection) {
            if (string.IsNullOrEmpty(text)) {
                return text;
            }
            byte[] buf;
            try {
                buf = CookieProtectionHelperWrapper.Decode(cookieProtection, text);
            }
            catch(Exception ex) {
                throw new InvalidCypherTextException("Unable to decode the text", ex.InnerException);
            }
            if (buf == null || buf.Length == 0) {
                throw new InvalidCypherTextException("Unable to decode the text");
            }
            return Encoding.UTF8.GetString(buf, 0, buf.Length);
        }
    }
}

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License

This article, along with any associated source code and files, is licensed under The Microsoft Public License (Ms-PL)

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About the Author

Adam Tibi
Architect
United Kingdom United Kingdom
Passionate about refining software practices, promoting self-motivated teams and orchestrating agile projects that hit the deadline.
Lives in London, UK and works as a .NET architect consultant in the City.

Need a pro service to help your organisation? Contact me via my website www.AdamTibi.net.
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